This application generally relates to a unique tire valve assembly as used in a vehicle central tire inflation system. More particularly, the invention relates to a tire valve assembly with an integrated pressure sensor for monitoring tire pressure for the central tire inflation system.
Maintaining proper tire pressure is important for maximizing tire life. Central tire inflation systems (CTIS) are used in vehicles to maintain proper tire inflation. Various types of central tire inflation systems are known in the art. One type of system can automatically inflate tires to a desired pressure level once the tire pressure has fallen below that level. Such a system includes an air supply tank that is pneumatically connected to a pressure regulator that is set to a predetermined pressure. This regulator is pneumatically connected to each of the designated tires on the vehicle. When a pressure drop in a tire is sensed via the regulator, air flowing from the outlet of the pressure regulator is supplied to the axle having the low-pressure tire. In one known configuration, the axle has an air inlet that leads to the interior of the axle, which serves as an air conduit to a rotary seal assembly that is installed at each wheel end on the axle. The rotary seal has a stationary part that is fixed to the axle, and a rotatable part that rotates with the wheel and includes a tubular member for connection to the valve stem on the tire mounted on the rim of the wheel.
Another type of CTIS system includes the dual capability of inflating tires to a desired pressure level and deflating tires to a desired lower pressure level to accommodate off-road terrain. One such system includes an air supply tank and conduits that connect the air supply tank to a pressure regulator, an inflate valve, a deflate valve, a shut-off valve, and a quick release valve. A control system is used to move inflate, deflate, and shut-off valves between open and closed positions. The system also includes a control valve and a low-pressure shut-off valve that are pneumatically connected to the interior chamber of the tire. Pressure transducers in the conduits are used to monitor the tire pressure.
These central tire inflation systems are complex and expensive. Also, these systems have difficulty in accurately measuring the tire pressure at each of the wheels. Thus, there is a tendency to continuously maintain a higher pressure than necessary from the air supply tank to the tire, which is damaging to the system seals.
Thus, it is desirable to have a CTIS system that provides a simplified method and device for accurately measuring tire pressure at the wheel. The system should also be inexpensive and be compatible with known central tire inflation systems.
In a disclosed embodiment, a valve stem for a vehicle tire includes an elongated body having a central bore extending through the body to define a first opening at one end of the body and a second opening at an opposite end of the body. A valve seat is formed within the bore and a valve member is supported within the bore. The valve member engages the valve seat such that fluid is prevented from flowing between the first and second openings. A pressure sensor is partially received in the bore and is used to measure fluid pressure at the first opening.
In a preferred embodiment, the valve stem has a Y-shaped configuration and is used in tires for a vehicle having a central tire inflation system. Each tire has a valve stem with the pressure sensor incorporated therein to measure the tire pressure. When the tire pressure falls below a desired level, the central tire inflation system fills the tire with fluid until a desired pressure level is achieved. The Y-shaped configuration is preferred because it is compatible with central tire inflation systems while still allowing external pressure checks.
In one disclosed embodiment, a method for monitoring pressure in a tire for a central tire inflation system includes the steps of providing a vehicle tire assembly having a valve stem with a centrally extending bore, a valve member movably supported within the bore, and a valve seat for seating the valve member to prevent fluid from flowing through the bore. A pressure sensor is installed within the bore and measures tire pressure. A signal representing the tire pressure is generated and sent to a central tire inflation system controller.
The subject valve stem provides a simplified method and apparatus for measuring tire pressure for a vehicle having a central tire inflation system and for relieving air seals from pressure when air is not being added to the tire. Further, the subject valve stem is easily incorporated into any of the know central tire inflation systems. These and other features can be understood from the following specification and drawings.